The present invention relates to a pulse generator and more particularly to a high voltage pulse generator, more particularly known in the art as a Marx generator.
The invention applies to the supply of high voltage pulses having a pulse front with a very fast rise time.
The prior art discloses high voltage pulse generators comprising cascade-connected cells, respectively having capacitors charged across resistors. The high voltage pulse is obtained at the generator output by bringing about the discharge of the capacitors across resistors, by means of spark gap switches connected to said capacitors. These spark gap switches are switched in cascade, e.g. using ultraviolet radiation. If the d.c. voltage applied to the generator input for charging the capacitors has a value Vo and if the generator has n capacitors, the voltage of the generator output pulse is equal to n.Vo.
In a more detailed manner, this type of high voltage pulse generator or Marx generator comprises, as shown in FIG. 1, a succession of spark gap switches E.sub.1, E.sub.2, . . . , E.sub.n-1, E.sub.n. Each of these spark gap switches, such as e.g. switch E.sub.1, comprises a first electrode 1 and a second electrode 2. The first electrode of each spark gap switch is connected to the first electrode of the following spark gap switch of said succession of spark gap gap switches by a first resistor in the case of spark gap switches of rank 1 to n-1. These first resistors are designated R.sub.1, R.sub.2, . . . , R.sub.n in FIG. 1. Thus, for example, resistor R.sub.1 connects the first electrode 1 of spark gap switch E.sub.1 to the first electrode 3 of spark gap switch E.sub.2. In the same way, the second electrode of each spark gap switch is connected by a second resistor to the second electrode of the following spark gap switch of said succession for spark gaps of ranks 1 to n-1. These second resistors are designated R'.sub.1, R'.sub.2, . . . , R'.sub.n in FIG. 1. For example, the second resistor R'.sub.1 connects the second electrode 2 of spark gap switch E.sub.1 to the second electrode 4 of spark gap switch E.sub.2. In addition, the second electrode of each spark gap switch is connected by a capacitor to the first electrode of the following spark gap switch of the succession of spark gaps for spark gaps of ranks 1 to n-1. These capacitors are designated C.sub.1, C.sub.2, . . . , C.sub.n-1, C.sub.n in FIG. 1. Thus, for example capacitor C.sub.1 connects the second electrode 2 of spark gap switch E.sub.1 to the first electrode 3 of spark gap switch E.sub.2.
The generator shown in FIG. 1 is applied by a d.c. voltage source 5, which is connected by a second resistor R' to a common point A between the second electrode 2 of spark gap switch E.sub.1 of rank 1 and the second resistor R'.sub.1 connecting said second electrode of spark gap switch E.sub.1 to the second electrode 4 of spark gap switch E.sub.2 of rank 2. The second electrode 7 of spark gap switch E.sub.n of rank n is connected to a first coating 9 of an output capacitor C, a first resistor R connecting the first electrode 6 of spark gap switch E.sub.n of rank n to a first coating 8 of output capacitor C. The output voltage of the generator shown in the drawing is a voltage of pulse type and which appears at the time of triggering the spark gap switches. This vol age can be applied to a load circuit L. It is available on the first coating 8 of output capacitor C. In the example shown in FIG. 1, the generator has n-1 capacitors if the input d.c. voltage applied by source 5 is equal to Vo, the output pulse voltage being equal to (n-1).Vo. In FIG. 1, M designates the reference earth.
The realization of a Marx generator of the type whose circuit has just been described generally takes place by using capacitors protected by a covering, equipped with a group of terminals making it possible to connect the different components of said circuit, e.g. paper capacitors. These capacitors are contained in metal or plastic boxes having insulators for the output terminals of the capacitors. It is also possible to use capacitors having ceramic dielectrics, said capacitors being sealed and consequently far from easy to manufacture.
Marx generators whose circuits are constructed in the manner described hereinbefore and which use paper capacitors contained in metal boxes or sealed ceramic dielectric capacitors suffer from the important disadvantage of a lack of compactness, as a result of the supplementary overall dimensions due to the coverings and connections. Thus, the electrical energy which can be supplied by the known Marx generators is reduced and the equivalent inductance of the generator is high, which is prejudicial to the power supplied.